1. Field of the Invention
This invention relates to a solid catalyst component for a catalyst which can produce stereoregular or stereospecific .alpha.-olefin polymers in a high yield. More particularly, this invention relates to a transition metal component for a Ziegler type catalyst which comprises a certain titanium compound supported on a halogen-containing magnesium compound.
2. Description of the Prior Art
It is known that a high-activity catalyst is obtained by using a certain titanium compound supported on a magnesium halide as a transition metal component which constitutes in combination with an organoaluminium compound a Ziegler type catalyst for polymerization of .alpha.-olefins (e.g., as disclosed in U.K. Pat. Nos. 1,286,869 and 1,292,853. .alpha.-olefin polymers produced with such catalysts, however, have very low stereoregularity or stereospecificity.
In order to solve the problems concerning low stereoregularity of the polymers polymerized with a solid catalyst component comprising such a supported titanium compound, the introduction of a variety of electron-donor compounds into such solid catalyst components has been attempted. It has been recently found that the incorporation of benzoates into such catalyst components markedly enhances the stereo-regularity of the resulting .alpha.-olefin polymers and that the catalytic activity is not lowered (e.g., reference is made to German Laid-open Pat. No. 2,230,672. U.S. Pat. No. 4,107,415 and 4,069,169. To the best of the inventors' knowledge, however, it does not seem that the activity of the catalyst and the stereoregularity of the resulting polymer have been enhanced by the above-mentioned improvement to an extent such as to eliminate the steps of removing catalyst residues from polymers and extracting atactic polymers. The benzoates are benzoate esters.